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Discussion Starter · #1 ·
Hey guys, I'm helping a friend out here so I'll try and fill in details as I go.

He's got a '97 F150 Lariat EC/SB 4x4 w/4.6L & AT. It's got ~107,000 miles, 90% of which are highway from Eastern WA to Western WA on the weekends. He's the second owner, bought it with 75k, has done a LOF every 3k miles since owning it. He just had the injectors cleaned, transmission flushed, coolant flushed, diffs changed, new platinum plugs & wires. Last year a new fuel pump and filter were installed. Aside from a set of tires he hasn't had to do much to it. The truck has the stock exhaust, and original intake (i.e. no K&N, or aftermarket)

The problem is his economy has gone from ~320 miles/tank down to just over 200 miles/tank, he hasn't changed the way he drives or where he drives. There is no check engine light on. He's mentioned to me that it doesn't have the snap it used to as well. Driving around town isn't as noticable, but out on the highway the slight grades that shouldn't bother it cause it to bog down somewhat. It idles smooth sitting in the parking lot, starts fine, no extended cranking.

Thank you in advance for any light you may be able to shed on this thing.
 

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Re: 97 F150 4.6L, loss of power & economy, no codes.

Jee theres a ton of stuff it could be...02 sensor? Clogged cattaltic converter?

Sounds stupid, but has he checked the air filter?
 
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Discussion Starter · #3 ·
Yeah, sorry to mention it got a new air filter with all the new fluids. Wouldn't a bad O2 sensor set a code? I've been considering the possibility that the cat is plugged, how would you check though?
 

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Re: 97 F150 4.6L, loss of power & economy, no codes.

You are correct, if everything is working right the O2 sensor SHOULD throw a code...doesnt mean it couldnt go bad without showing one.

I dont know of any other way to check the cat except remove it and look. Even then you may just have to resort to puting a new one on and seeing if there is a difference.
 
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Discussion Starter · #5 ·
97 expedition 5.4

hey there im having the same prob ive changed 8 coils the cats all of the 02 sensor the 2 filters where the first thing i changed
 
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